1. Field of the Invention
The present invention relates to a semiconductor memory device, and more particularly, to a semiconductor memory device which is capable of writing a data simultaneously to a plurality of memory cells.
2. Description of the Prior Art
Recently, a dynamic random access memory (DRAM) for video (VRAM) which utilizes the DRAM technology and is suitable as a video memory has been developed and is in widespread use. The arrangement location of a data stored in a VRAM corresponds to a display screen. For example, a data in a memory cell group on the same word line corresponds to one line portion (one scanning line portion) of the display screen. As the case may be, all of the regions for the portion of several lines of the display screen have the same color. In such a case, it takes too long a time if a data is written to each memory cell in order to make these cells to have the same color. To solve this problem, a technology for writing the same data at once to the memory cell group belonging to the same word line has lately been developed.
However, the conventional structure for writing an identical data all at once to the memory cell group belonging to the same word line requires special circuits such as a special purpose circuit for supplying an identical data to every bit line, a special decorder circuit which realizes the simultaneous selection of all of the bit lines or a control circuit which controls the decoder circuit. Along with the increase in the memory capacity, there is generated a problem in that the scale and the area of these circuits are increased correspondingly.